Managing electric fields generated in vehicles has long been a consideration when building vehicles with internal combustion engines. Any time current is generated in an electrical system, there is also a subsequent electric field related to the current generation. These fields can interfere with other electrical components and systems in a vehicle.
Certain electrical components are more sensitive to the fields than others. For instance, in operating a vehicle radio on AM or FM bands, spark plug interference is prevalent at times. Resistance spark plugs knocks down the interference as well as using spark plug wires designed to reduce background electrical noise.
As vehicle systems and society in general become increasingly reliant on electrical controls and monitoring cages and systems, the need to further manage and limit electromagnetic interference has also become much more important and even critical to ensuring correct operation of electrical devices in or in close proximity to the vehicle.
With the advent of electric hybrid and pure electric powered vehicles, the current used in such vehicles is magnitudes more than used in conventional vehicles. The motors used and the batteries, wires, relays solenoids and other components must be extremely robust in order to effectively and reliably handle the electrical energy necessary to power and run the systems in the vehicle. Therefore, the electric fields produced by these systems have increased. While modern engineering and materials have helped control some of the electrical field emissions, there remains a need to further control and or shield or isolate gauges, radios, lighting, and occupants from the electrical fields generated.
In particular, most EV batteries, battery management systems, traction motor controllers and DC-DC converters are connected to devices or are devices that are switching high power (up to 100 kW or more) at high frequencies (20-50 kHz). This results in electromagnetic fields, at these frequencies and harmonics, that may radiate from the devices and these radiations could interfere with safety, communication, and entertainment equipment. This could occur both on board and off board the vehicle. The allowable level of emissions is controlled through regulation (e.g., FCC) and product performance specifications.
Standard practice in enclosure design is to use metals or coat plastic or composite enclosures with metal. Semi-structural battery housings used in these vehicles have used glass reinforced SMC with a shielding layer, typically copper. This is a robust yet expensive and heavy solution. Therefore, there remains a need in the art to replace heavy and expensive copper shielding designs with a more cost effective and lighter material without sacrificing shielding characteristics.